Different types of acoustic devices have been used through the years. One type of acoustic device is a microphone, and one type of microphone is a microelectromechanical system (MEMS) microphone. In a MEMS microphone, a MEMS die includes a diagram and a back plate. The MEMS die is often disposed a substrate (or base) and is enclosed by a housing (e.g., a cup or cover with walls). A port may extend through the substrate (for a bottom port device) or through the top of the housing (for a top port device). In any case, sound energy traverses through the port, moves the diaphragm and creates a changing potential with respect to the back plate, which creates an electrical signal. An application specific integrated circuit (ASIC) may perform further processing on the signal. Microphones are deployed in various types of devices such as personal computers or cellular phones.
Unfortunately, previous approaches have limitations. Electrical audio systems include various power-consuming elements such as codecs. High amounts of power are consumed because the codec is typically always on for signal processing. Additionally, a limited bandwidth for ultrasonic frequencies is provided by these previous approaches depending upon the sampling rate of the codec.
All of these problems have resulted in some user dissatisfaction with previous approaches due to high power consumption and reduced battery life.
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